High-performance liquid chromatography determination of direct and temporary dyes in natural hair colourings.

A simple and reliable HPLC method is described for the simultaneous determination of nine direct and temporary hair dyes in hair colourings containing vegetal extracts. Detection was performed by a diode array detector and two different wavelengths, in the visible range (450 and 650 nm), were used for quantitation. The method does not involve any extraction procedure and it is sufficiently rapid and accurate for routine analyses. The method described was successfully applied to the identification of synthetic organic dyes in 13 direct and temporary hair dyeing formulations commercialized as 'natural'.